Bragg Gratings in Two-Core Rectangular Fiber for Discrimination of Curvature, Strain, and Temperature Measurements
Lin Htein, Dinusha Serandi Gunawardena, Chern Yang Leong, Hwa‐Yaw Tam
Abstract
We report, for the first time, the development of a rectangular fiber with two cores consisting of different refractive indices for the discrimination of temperature effects during strain or curvature measurements using fiber Bragg gratings written in a single segment of fiber. Two cores with a diameter of 8 μm and a rectangular cladding with dimensions of 120 μm × 255 μm permit convenient splicing to conventional single-mode fiber and support easy identification of the orientation of the fiber. When placed in the desired orientation, each core of the two-core rectangular fiber experiences a different spectral shift in the presence of applied strain or curvature. The sensitivities of the two cores are 0.87 and 1.08 pm/με for strain, 126 and -128 pm/m <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> for curvature, and 10.05 and 10.40 pm/ <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">o</sup> C for temperature, respectively. In addition, the flat cladding structure of the fiber provides a large physical contact area between the sensing fiber and the substrate than a circular fiber and allows better strain coupling between the object and the fiber.